José Manuel NievesSEGUIRMadrid Updated: Save Send news by mail electrónicoTu name *
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Makes 360 million years, an event unknown caused the rapid disappearance of a large part of the plants and the freshwater species of the Earth. Now, a team of researchers from the british university of Southampton has discovered that the “culprit” was the collapse of the ozone layer that protects our planet from harmful ultraviolet radiation. The finding, recently published in Science Advances, has profound implications for the world today.
During the long history of life on Earth, there have been a number of great mass extinctions. Today, we know that one, the one that killed the dinosaurs makes 66 million years ago, was caused by the impact of a meteorite. Others, such as the one that took place in the Permian makes 252 million years ago, due to huge massive volcanic eruptions on a continental scale.
And now, this study shows that also a high level of uv radiation can collapse the forest systems and killing many aquatic species, such as fish and terápodos (our distant ancestors), who lived in the Devonian period, ago to 359 million years ago. On this occasion, therefore, there were no meteors nor rash, but a large hole in the ozone layer caused by a sudden global warming right after an intense ice age. Does it sound like them?
it Is inevitable, in fact, compare that situation with the current, and the researchers suggest in their study that in a very short time, the Earth could reach temperatures comparable, what is likely to trigger a similar event.
For their research, the scientists collected rock samples in the polar regions mountain eastern Greenland, which in those times formed the bed of an ancient lake in the arid interior of a continent that included the current Europe and North America. The lake, in the southern hemisphere of the planet, could be similar to the current lake Chad, on the edge of the Sahara desert.
were Also collected from the rocks of the andes mountains on lake Titicaca, in Bolivia. These samples are from the old continent south of Gondwana, which in the Devonian was closer to the South Pole. In this way, the researchers obtained clues to what was happening at that very moment, both near the South Pole as at the equator.
once in the laboratory, the rocks were dissolved in hydrofluoric acid, thus liberating the spores of microscopic plants such as ferns, preserved in the interior of rocks for hundreds of millions of years. The microscope, the scientists discovered that many of these spores had a strange spines on its surface, a way of responding to the ultraviolet radiation that damaged their DNA. In addition, many spores had a sort of “walls” of dark pigment, which the scientists consider as a kind of “tan” protective against the increased UV rays.
The conclusion was that during that period of rapid global warming, the ozone layer collapsed during a period of time, exposing the life of the planet to harmful levels of ultraviolet radiation and causing a major mass extinction event on land and in shallow water. The deadly event took place 360 million years ago, at the boundary that separates the Devonian from the Carboniferous.
So disappeared the ozone
After melting the ice caps, the climate warmed rapidly, and that rising temperatures pushed up to the upper atmosphere chemicals capable of destroying ozone, which caused a hole that let them in, for several thousands of years, a large amount of ultraviolet radiation.
John Marshall, of the School of Science of the Ocean and the Land of the University of Southampton and director of the study, explains that “the shield of ozone disappeared for a while in this ancient period, coinciding with a brief and quick warming of the Earth. Naturally, our ozone layer is always in a state of flux, being created and being lost constantly, and we have shown that this also happened in the past and without the need of a catalyst, such as a volcanic eruption on a continental scale”.
During extinction, some types of plants managed to survive, but their cycles were altering severely as the forest ecosystem collapsed. The then dominant group of fish-armored is completely extinguished and the bony fish that survived, like the sharks, became from then on the fish dominant of our ecosystems.
Our forefathers, affected
The extinction, in addition, it came at a key moment for the evolution of our own ancestors, the terápodos. The first terápodos, in effect, were fish that evolved to have limbs instead of fins, thanks to which were able to take their first steps out of the water. It was creatures still eminently aquatic and whose limbs they had a large number of fingers in hands and feet. The extinction redirected, its evolution, and those that survived were better adapted they were to live out of the water. Creatures already fully terrestrial, and with the number of fingers of hands and feet reduced to five.
To Marshall, these findings have a number of surprising implications for the present life on Earth: “The current estimates -ensures – suggests that we achieve overall temperatures similar to ago, 360 million years, with the possibility of a similar collapse of the ozone layer could occur again, exposing the earth’s surface and the marine life of the surface to a radiation deadly. That would take us to the current state of climate change in a real weather emergency”.
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